EVALUATION OF FATIGUE DAMAGE IN STEEL STRUCTURAL COMPONENTS BY MAGNETOELASTIC BARKHAUSEN SIGNAL ANALYSIS

This paper is concerned with using a magnetic technique for the evalua tion of fatigue damage in steel structural components. It is shown tha t Barkhausen effect measurements can be used to indicate impending fai lure due to fatigue under certain conditions. The Barkhausen signal am plitude is known to be highly sensitive to changes in density and dist ribution of dislocations in materials. The sensitivity of Barkhausen s ignal amplitude to fatigue damage has been studied in the low-cycle fa tigue regime using smooth tensile specimens of a medium strength steel . The Barkhausen measurements were taken at depths of penetration of 0 .02, 0.07, and 0.2 mm. It was found that changes in magnetic propertie s are sensitive to microstructural changes taking place at the surface of the material throughout the fatigue life. The changes in the Barkh ausen signals have been attributed to distribution of dislocations in stage I and stage II of fatigue life and the formation of a macrocrack in the final stage of fatigue.